The present invention relates to a process for the preparation of fulvene-metal complexes, new fulvene-metal complexes and their use as catalysts for the polymerization of unsaturated compounds, in particular for the polymerization and copolymerization of olefins and/or dienes.
Metal complexes with cyclopentadienyl ligands have been the subject of intense investigation since the discovery of ferrocene. The use of cyclopentadienyl-metal complexes, in particular the use of metallocene complexes as a mixture with activating cocatalysts, preferably alumoxanes, for the polymerization of olefins and diolefins has been known for a long time (e.g. EP-A 69 951, 129 368, 351 392, 485 821, 485 823). Metallocenes have proved to be highly active, specific catalysts in the polymerization of olefins. A large number of new metallocene catalysts and metallocene catalyst systems for the polymerization of olefinic compounds have therefore been developed in recent years in order to increase the activity, selectivity, control of the microstructure, molecular weights and molecular weight distribution.
Comparatively little is known of metal complexes with fulvene ligands.
J. Am. Chem. Soc. 1997, 119, 5132 describes zwitter-ionic olefin polymerization catalysts which are formed in the reaction of specific (xcex76-2,3,4,5-tetramethylcyclopentadienyl-1-methylene) (xcex75-pentamethylcyclopentadienyl)zirconium compounds with tris(pentafluorophenyl)boron or bis(pentafluorophenyl)-borane. The synthesis of the (xcex76-2,3,4,5-tetramethylcyclopentadienyl-1-methylene)(xcex75-pentamethylcyclopentadienyl)zirconium compound is very expensive, it first being necessary to prepare a metallocene with pentamethylcyclopentadienyl ligands, which is decomposed by a thermolysis reaction in the last synthesis stage. Such thermolysis reactions are described in the literature.
According to Bercaw et al., JACS (1972), 94, 1219, the fulvene complex (xcex76-2,3,4,5-tetramethylcyclopentadienyl-1-methylene)(xcex75-pentamethylcyclopentadienyl)titanium-methyl is formed by thermolysis of bis(xcex75-pentamethylcyclopentadienyl)titanium-dimethyl. T. J. Marks et al., JACS (1988), 110, 7701 describe the thermolysis of pentamethylcyclopentadienyl complexes of zirconium and hafnium. The fulvene complex (xcex76-2,3,4,5-tetramethylcyclopentadienyl-1-methylene)xcex75-pentamethylcyclopentadienyl)zirconium-phenyl is formed by thermolysis of bis(xcex75-pentamethylcyclopentadienyl)zirconium-diphenyl.
The preparation of fulvene complexes by the thermal process is limited to a few structural variants. The thermal process does not always lead to uniform products.
G. Wilkinson et al. in J. Chem. Soc. 1960, 1321-1324 describe the reaction of 6,6-dialkylfulvenes with chromium-hexacarbonyl or molybdenum-hexacarbonyl. However, cyclopentadienyl-metal complexes are obtained instead of the fulvene-metal complexes.
In J. Chem. Soc. Dalton Trans. (1985), 2037, M. L. H. Green et al. report the synthesis of bis(xcex76-6,6-diphenylfulvene)titanium by reaction of bis(toluene)titanium with 6,6-diphenylfulvene. However, the bis(toluene)titanium must be prepared by involved and expensive metal atom vaporization techniques. For this, metallic titanium is vaporized and condensed in a matrix together with gaseous toluene. The yield of bis(toluene)titanium is very low. The bis(toluene)titanium is therefore accessible to only a limited extent.
There was therefore the object of discovering an improved process for the preparation of fulvene-metal complexes which avoids the disadvantages mentioned.
It has now been found, surprisingly, that fulvene-metal complexes can be prepared by reaction of a fulvene compound with a suitable transition metal complex in the presence of a reducing agent.